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From: dave@westmark.westmark.com (Dave Levenson)
Newsgroups: comp.dcom.telecom
Subject: Re: CLID Compatibility Question
Message-ID: <16226@accuvax.nwu.edu>
Date: 20 Jan 91 03:37:44 GMT
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X-Telecom-Digest: Volume 11, Issue 52, Message 4 of 7


In article <16200@accuvax.nwu.edu>, winslade@zeus.unomaha.edu (JOHN
WINSLADE) writes:

> Also, I had the impression that the Class-Mate was more or less a
> passive device that demodulated the CLID data and converted it to
> RS-232 compatible levels, and did not really do any heavy-duty data
> conversion.  Am I correct in assuming this.  Thanks.

The ClassMate appears to be a little more intelligent than that.  When
it is powered up, it outputs a four-line message in ASCII identifying
itself, giving its firmware copyright notice and version information.
It validates the checksum passed by the telco, but does not pass it
along to the RS-232 port.  It does pass a single character indicating
the validity of each message.

It appears to contain a modem (really, just a -dem) to demodulate the
incoming caller id information, a buffer memory for one message, and a
UART to talk to the RS-232 port.  There is probably also a
microprocessor that runs this stuff.  It most-likely consists of a
microcomputer -- one chip that contains ROM, RAM, and two serial
ports.  With such a device, one only needs the modem and the passive
components to drive the serial port at RS-232 levels.


Dave Levenson		Internet: dave@westmark.com
Westmark, Inc.		UUCP: {uunet | rutgers | att}!westmark!dave
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